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The Ultima TPS MoM THR was designed and developed as a 2nd generation MoM THR specifically aimed at younger more active patients due to the anticipated low wear rates and increased longevity of MoM THRs. In 2010, published clinical data highlighted the early failure of the Ultima TPS MoM due to fretting-crevice corrosion at the stem–cement interface. Since 2010 similar observations have been reported by other clinical centres implicating competitor products as well as the Ultima TPS MoM THR. In an attempt to replicate the electrochemical reaction and interactions established across MoM THR systems, fretting-crevice corrosion tests subjected to galvanic coupling were conducted. Galvanic coupling was seen to significantly increase the rates of corrosion under static and dynamic conditions. This was due to the large potential differences developed across the system between active and passive areas, increasing the rates of corrosion and metallic ion release from the stem–cement interface. [ABSTRACT FROM AUTHOR]

Abstract: In order to investigate the effect PMMA bone cement chemistry has on the fretting corrosion of cemented femoral stems, a novel test setup with integrated electrochemistry was developed and conducted in part reference to ISO 7206-4:2010. Ultima TPS™ femoral stems were cemented into a specially prepared delrin moulds using a third generation cementing technique similar to the procedure used in-vivo. Three commercially available PMMA bone cements were tested in order to understand the role bone cement chemistry plays on the fretting-corrosion rates at the stem-cement interface. Each stem-cement component was then orientated and set in place using laboratory grade PMMA cement, immersed in 0.9% NaCl and subjected to 500,000 cycles of cyclic loading at 1Hz. Intermittent Open Circuit Potential (OCP) and Linear Polarisation Resistance (LPR) measurements were conducted in order to assess the effect PMMA bone cement chemistry has on the localised dissolution of cemented femoral stems. Macroscopic observation and scanning electron microscopy with integrated energy dispersive X-ray analysis (SEM/EDX) was conducted in order to support the electrochemical findings. [Copyright &y& Elsevier]